1. Field of the Invention
This invention relates to the field of molecular biology and, in particular, to nucleic acid molecules encoding an Rb-interacting zinc finger (RIZ) protein and a conserved domain of a RIZ protein that is involved in regulating gene transcription.
2. Background Information
The retinoblastoma Rb protein is known to play a key role in controlling normal cell proliferation and differentiation. The ability of a cell to divide requires the cell to pass through the various phases of the cell cycle. Although Rb is believed to keep normal cells from dividing by maintaining them in a phase of the cell cycle known as G.sub.1 or G.sub.0, the precise mechanism underlying Rb function is unknown. It is known, however, that Rb can bind various cellular proteins, including proteins involved in regulating gene transcription. Thus, Rb may exert its action by interacting with such cellular proteins.
The role that Rb plays in controlling cell growth makes it an attractive target for promoting the growth of tissues that normally do not grow because of the action of Rb. For example, cardiac muscle tissue and nervous tissue that have lost function due to cell death are not usually repaired by subsequent proliferation of the remaining live cells. Thus, a method to block the growth controlling function of Rb can be useful for inducing tissue repair in situations of cardiac or neural cell death.
Rb also is known as a tumor suppressor since the abnormal growth of a cancer cell can result from inactivation of Rb protein. Such inactivation can occur either due to a mutation or to inactivation of Rb protein subsequent to binding a viral oncoprotein, a product of an oncogenic tumor virus. A particular region in Rb called the Rb pocket appears to be critical for its growth controlling function since Rb inactivation by mutation or by oncoprotein binding impacts this region.
The importance of the Rb pocket in the functioning of Rb and the understanding that viral oncoproteins can regulate Rb by binding the pocket suggest that there may be normal cellular proteins that can regulate the function of Rb by binding the pocket. The identification of such proteins will provide new approaches to regulate the control of cell proliferation mediated by Rb in diseases such as those that involve loss of cardiac or neural function or in the control of cancer.
Thus, a need exists to identify proteins that can bind to and regulate Rb in order to provide new approaches for controlling cell proliferation and differentiation. The present invention satisfies this need and provides related advantages as well.